Electromagnetic contactor



July 10, 1934. PiERCE ELECTROMAGNETIC CONTACTOR Filed May 20, 1930 2 Sheets-Sheet l INVENTOR A awrence P/erca ATTORNEY July 10, 1934. PlERCE ELECTROMAGNETIC CONTACTOR Filed May 20', 1930 2 Sheets-Sheet 2 INVENTOR L awrence H'erce.

AITTORNEY Patented July 10, 1934 UNITED STATES PATENT OFFICE ELECTROMAGNETIC CONTACTOR Application May 20, 1930, Serial No. 453,988

7 Claims.

My invention relates, in general, to electromag netic contactors and, more particularly, to are rupturing devices provided on contactors to extinguish the are drawn between the contact members when they are separated while carrying current.

An object of my invention, generally stated, is to provide a contactor that shall be simple and emcient in operation, and which may be readily and economically manufactured.

A more specific object of my invention is to provide a contactor that shall have a high current-interrupting capacity.

Another object of my invention is to prevent burning of the contact members, the arc horns and the arc box.

Still another object of my invention is to so confine an arc, travelling along the surface of an arc horn, that the arc voltage will be raised to a value that will cause the arc to restrike to the surface of the arc horn with a result that a process of lengthening the arc and then extinguishing a portion of it is continuously carried on until the arc is interrupted.

In a direct-current contactor, the arc may be extinguished by so lengthening and confining it that the arc requires, for its maintenance, a voltage higher than is generated in the direct-current circuit. The current then decreases, and, if the voltage required by the arc remains higher than the generated voltage, the current is reduced to zero, and the arc is extinguished.

According to my invention, a magnetic field is provided which drives the are along the surfaces of the arc horns, carried by the contact members, and into spaces or pockets provided between the arc horns and insulating cross members which also serve, as spacers, to separate the sides of the arc box. The confining of the are in the pocket thus formed raises the voltage of the are per unitlength and hence raises the voltage, required to maintain the arc, to a value higher than the voltage generated in the circuit, thus extinguishing the arc. Also, the arc is prevented from burning the arc-receiving parts of the contactor as the arc terminals are kept moving along the surfaces of the arc, horns.

For a fuller understanding of the nature and objects of the invention, reference may be had to the following detailed description, taken in conjunction with the accompanying drawings, in which:

Figure l is a view, in front elevation, of an electromagnetic contactor constructed in accordance with my invention.

. bers.

Fig. 2 is a view, partly in side elevation and partly in section, of the contactor shown in Fig. 1, and

Fig. 3 is a view, partly in side elevation and partly in section, of a modification of the invention,

Referring to the drawings, the entire contactor mechanism is mounted upon an insulating panel 10. An electromagnet 11, having a pivotally fl mounted armature 12, is provided for actuating a movable contact member 13 into engagement with a fixed contact member 14.

In order that the correct contact pressure may be maintained between the contact members, the movable contact member 13 is resiliently mounted on the armature 12. The fixed contact member 14 is mounted on an insulating base 15. which is carried by a bracket 16, mounted upon the panel 10. 4

As is the usual practice, are horns 17 and 18 are mounted on the contact members 13 and 14, respectively. A flexible shunt 19 is provided for conducting current from the movable contact member 13 to the connecting stud 20.

In order to provide a magnetic field for forcing 30 the arc, which is drawn between the contact members 13 and 14, away from the contact members and for causing it to travel along the surfaces of the arcing horns, an electromagnetic blowout coil is mounted above the contact mem- 35 The blowout coil comprises a coil 21 which is wound around a core 22. Metallic plates 23 are mounted at the sides of the coil and serve as pole pieces to complete the magnetic circuit. As shown, one end of the coil 21 is connected to a stud 24, and the other end of the coil is connected to the fixed contact member 14.

With a view to confining the are within substantially definite limits to prevent it from striking and burning the current-carrying parts of v the contactor, it is necessary to provide an arc box 25 which substantially encloses the contact members 13 and 14 and also the arcing horns 17 and 18. The are box comprises sides 26 which are separated by cross members 27 and 28. It may be constructed of an insulating, refractory material, as, for example, soap stone.

By referring to Fig. 2, it will be observed that the insulating cross member 28 is mounted above the arcing horn 18. In this embodiment, the

1 arcing horn 18 is curved around the blowout coil 21, in order to provide a space or pocket 29 between the cross member 28, the sides 26, and the horn 18 into which the arc is forced by the magnetic field produced by the blowout coil 21.110

the back.

A space is also provided between the cross member 27 and the arcing horn 1'7 when the contact member 13 is in the open position.

In order to provide for inspection and replacement of parts of the contactor the arc box 25 is pivotally mounted at the top by a pin 31, and the box may be easily raised about the pivot point. 1

When the magnet 11 is energized, the armature 12 is biased upwardly, and the contact member 13 is actuated into engagement with contact member 14. An electrical circuit is then completed from the connecting stud 24, through the blowout coil 21, contact members 14 and 13 and the flexible shunt 19, to the connecting stud 20. When the magnet 11 is deenergized, the contact member 13 drops to the position indicated by the broken lines. Upon interruption of the electrical circuit by the separation of the contact members 13 and 14, an arc is drawn between the contact members, and the current traversing said members is directed through the arc which acts as a conductor. A magnetic field is created by the blowout coil which affects the arc in a man ner similar to the force exerted upon an armature conductor in the field of an electric motor. The magnetic circuit is so designed that the magnetic field, created by the blowout coil, will direct the are away from the contact members and force the arc terminals to travel along the surfaces of the arcing horns. The path of the arc, as it progresses along the surface of the horns, may be represented by the dotted lines 32, 33 and 34:, respectively.

It may be seen that the arc is lengthened as it is driven along the arcing horns and is forced into the spaces 29 and 30. The are is confined between the sides 26 of the arc box, the insulating cross members 27 and 28 and the arcing horns 17 and 18. This raises the arc voltage per unit length, and hence, raises the voltage required to maintain the arc. The are terminal will. continue to travel, along the surface of the horn, into the space 29 until the arc voltage is raised to a value that will cause the arc to restrike to the surface of the horn approximately at the point where the arc enters the pocket 29. This process is repeated until the stored energy of the circuit is dissipated, and then the arc is extinguished. Burning of the arc horn is prevented, as the arc terminal is kept rapidly moving along the surface of the horn. Further, the

arc box 25 prevents the are from striking the current-carrying parts of the contactor, while the arc is being extinguished.

A modification of the invention is shown in Fig. 3. Parts having similar functions are designated by the same reference characters. It may be seen that the principal difference between the contactor illustrated in Fig. 3 and the one shown in Fig. 2 is the shape of the arc horn 18 and the location of the blowout coil 21 and the cross member 28. It will be observed that in Fig. 3, the pocket or space 29 is provided between the bac of the horn and the cross-member 28.

In this instance. the arc terminal travels up the front down the back of the horn 18 into the space provided between the horn and the insulating barriers. As the arc terminal transfers iron the front to the back of the horn, the direction of the current, conducted by the arc, eifectively changes, and the magnetic field, created by the blowout coil 21, which drove the arc up the front of the horn will drive it down Consequently, the arc is extinguished in a manner similar to that previously explained.

The advantages of equipment of the character described will be vident to those familiar with the art. The principles of a single blowout magnet are well known, but I have provided a magnet that produces a magnetic field which drives the arc terminals away from the current-carrying portions of he switch mechanism into special pockets. thereby causing the arc to be extinguished and, at the same time, I have succeeded in confining the are within substantially definite limits. I have also prevented burning of the arcing parts of the contactor by keeping the arc moving rapidly over these parts.

Since numerous changes may be made in the above-described construction and different embodiments of the invention may be made without departing from the spirit and scope thereof, it is intended that all the matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense. I

I claim as my invention: 7

1. An arc-rupturing device comprising, in combination, a plurality of contact members disposed for relative movement, an arc box comprising sides and cross members disposed in spaced relation, arc horns carried by the contact members and disposed between the sides of the arc box to form pockets between the horns and cross members, said pockets having a depth of at least twice their thickness, and electromagnetic means for producing a magnetic field to force the are drawn between the contact members to travel.

along the horns and into the pockets provided between the horns and the cross members of the arc box.

2. An arc-rupturing device comprising, in combination, a plurality of contact members, are

horns carried by the contact members, an arc box substantially enclosing the arc horns, said are box having a cross member disposed in predetermined relation to one of said arc horns to form a pocket having a wedge-shaped opening,.,

said pocket having a depth of at least twice its thicl iess, and electromagnetic means for producing a magnetic field to drive the are drawn between the contact members away from the contact members and along the surface of one of said horns into the pocket provided between the horn and the cross member of the arc box.

3. An arc-rupturing device comprising, in combination, a plurality of contact members, arc

horns carried by the contact members, an arc box. substantially enclosing the are horns and com-' prising sides and cross members disposed in spaced relation, said cross members being disposed in predetermined relation to the arc horns to form pockets having wedge-shaped openings,

said pockets having a depth of at least twice their thickness, and electromagnetic means for producing a magnetic field to force the arc drawn between the contact members to travel along the horns and into the pockets provided between the,

a substantially rectangular cross section is formed. between the horn and the barriers which will raise the voltage of an are travelling along the surface of the horn to a value that will cause the arc to restrike to the surface of the horn approximately at the point where the. arc enters the pocket.

5. In an arc-rupturing device, in combination, means for receiving the ends of an arc, means for causing the ends of the arc to travel along the arc-receiving means, and means for forming a relatively deep and narrow pocket of a substantially rectangular cross section for causing the arc to restrike the arc-receiving means and extinguish a portion of the arc.

6. An arc-rupturing device comprising, in combination, a plurality of contact members disposed for relative movement, an arc box comprising sides and cross members disposed in spaced relation, are horns carried by the contact members and disposed between the sides of the arc box, one of said horns being shaped to form a deep and narrow pocket of a substantially rectangular cross section and having a wedge-shaped opening between the horn and one of said cross members, and electromagnetic means for producing a magnetic field to force one end of the are drawn between the contact members to travel along the horn and into the pocket provided between the horn and the cross member of the arc box.

7. An arc-rupturing device comprising, in combination, a pair of contact members disposed for relative movement, an arc box comprising sides and cross members disposed in spaced relation, a curved arc horn connected to one of said contact members and disposed between the sides of the arc box to form a deep and narrow pocket having a wedge-shaped opening between said horn and one of said cross members, a triangularshaped horn connected to the other of said contact members and disposed between the sides of the arc box to form a similar pocket between said horn and one of said cross members when said contact member is in the open position, and electromagnetic means for producing a magnetic field to force the are drawn between the contact members to travel along the horns and into the pockets provided between the horns and the cross members of the arc box.

LAWRENCE PIERCE. 

